There are numerous means for removing particle matter from atmospheric air before introducing said air into a heating, venting, and/or air conditioning system. Typically, these systems have one or more removable and replaceable rigid filter elements which are manufactured to a specific length and height and inserted into a channeled filter housing to effectively seal the unit from the introduction of dust, dirt, and pollen.
Over time, contaminants build up on the filter media, thus necessitating replacement of the filter element. This typically requires the field technician to purchase a filter element from the original equipment manufacturer or a third party supplier. This system often leaves the technician with little choice but to stock every or most conceivable filter elements and to carry them from job site to job site. The alternative is to order the replacement filter element and schedule a second on-site maintenance call to install the element when it arrives.
In addition, replacement filter elements frequently allows significant contaminated airflow to circulate around the replaceable filter elements due to variations in tolerances between the replaceable filter elements and the original equipment manufacturers' channeled filter housing. As a result, the field technician usually is forced to clean the air conditioning system and the attached ductwork and air distribution registers much more frequently than necessary if a proper air seal integrity were achievable. This condition also decreases the mechanical and thermodynamic efficiency of the original equipment manufacturer's air conditioning system.
Further, the standard cardboard superstructure employed to give rigidity to replacement filter elements may result in the rigidity deteriorating during high humidity conditions or rainstorms. The replacement filter element may then be drawn out of the air conditioning system's channeled filter housing and into the air-moving fan, thus destroying the replaceable filter element's ability to filter. Use of the cardboard superstructure also blinds a portion of the replaceable filter element and reduces the capacity of the filter element to capture and retain particulate matter. And finally, use of cardboard superstructure requires the use of wood fiber and is not environmentally conservative.
A solution to several of these problems was presented in Culwell, U.S. Pat. No. 6,152,980, the specification of which is incorporated herein by reference. Culwell describes an air filter element that is partially fabricated on site. Instead of a cardboard superstructure, one or more wire frames are overlapped and rigidly fastened together using a high tensile strength adhesive tape to form a structure substantially conforming to the dimensions of the original equipment manufacturer's filter housing. The filter media is attached to the rigid wire frame by selective drawing pleated filter material around a portion of a wire member and securing the pleats to each other by means of epoxy coated staples.
Nevertheless, several problems still remain. Some equipment, such as supermarket refrigeration units, require long air filter elements. However, such equipment often is installed in such a manner where access to the filter housing is limited in space, so that a replacement air filter of the proper length cannot be inserted into the filter housing without moving the unit or neighboring equipment. Furthermore, problems have been found with the ends of the filter element being exposed during shipping, assembly and insertion, resulting in damage to the filter element and injury to the individual doing the installation.
Thus, what is needed is an improved means to fabricate a foldable or flexible filter element on-site with limited access space, on an as-needed basis and in a custom size providing a positive seal, with greater ease of assembly in the field and protection for the ends of the filter element.